Many of today's mobile terminal users have subscribed to more than one mobile communication service. For instance, such a user could have one private and one work-related subscription. In another case, such a user could have two different subscriptions for use in different areas (e.g., countries).
Accordingly, dual SIM devices become increasingly popular. A dual SIM device is typically realized in the form of a mobile terminal which is capable of holding two SIM cards. Dual SIM operation allows the use of two subscriptions without the need of carrying two mobile terminals. For example, the same mobile terminal can be used for business and private purposes with separate numbers (and bills) or for travel, with an additional SIM for the country visited.
The most common dual SIM devices are those of the dual standby-type, i.e., the device can—in standby—camp on two public land mobile networks (PLMNs) or cells, one for each active SIM. Furthermore, it is expected that multi-standby SIM devices capable of handling more than two SIM cards will be on the market soon.
US 2009/0215452 A1 may be construed to disclose a method and a mobile terminal according to the preambles of claims 1 and 14.
CN 101 198 136 A outlines a cell reselecting method for a dual SIM device. The method may be construed to comprise the following steps: A mobile telephone with dual SIM capabilities tests the signal intensity of adjacent cells corresponding to a SIM #1. If the SIM #1 meets a reselecting condition, a reselecting flow is started. For a SIM #2 a reselecting flow is independently completed. If the two SIMs belong to the same operator, the other SIM can share measurement parameters. This approach ensures that the dual SIM device can simultaneously support the cell reselection of the two SIMs when only one independent GSM communication module exists.
However, dual standby SIM devices not only need to listen on paging for each SIM, but also need to perform cell search and neighbor cell measurements on detected cells for mobility purposes for both PLMNs (i.e., to evaluate possible cell handover candidates). Accordingly, these operations will affect the standby time in idle mode. For instance, assuming the same DRX cycle for both PLMNs the device is camping on, typically a reduction of standby time by 50% is observable compared to a single SIM terminal. This could severely affect the user experience.
US 2009/0093217 A1 may be construed to disclose a channel measurement method for measuring signal strengths on designated channels, and for arranging the channels in an order of the signal strengths.
US 2009/0312020 A1 may be construed to disclose a method for searching/registering a cell in a first and a second network pertaining to a first and a second SIM card, respectively, wherein the searching/registering with the cell of the second network is performed during a non-paging duration of the first network.
CN 101 217 743 A may be construed to disclose a method for searching one and the same network for a first SIM in a mobile phone. Once a second SIM in the mobile phone intends to search the network, the second SIM reads the entire record without further measurement.
WO 03/101140 A1 may be construed to disclose a method for determining a geographic location of a mobile device. When in fingerprinting mode, signals strengths are measured for each available frequency band per location, and a location fingerprint is stored. When in the location mode, the signal strengths of all available frequency bands are measured, the measurement result is matched against the stored fingerprints, and the location is estimated based on the best match.